This invention relates to the subject matter of Disclosure Document No. 137,928, filed May 20, 1985.
A market limiting weakness of caliper disc brakes, for example, is the capability of the brake lining to withstand a limited temperature range before the liner bond begins to deteriorate and become detached from the backing surface of the metal shoe. Heretofore, to overcome this problem the liner was frequently riveted to the backing surface; however, such a procedure was undesirable because the wear volume and the surface area of the liner were significantly reduced. Another prior approach to overcoming the problem of attachment of the liner to the backing surface was to have the shoe surface provided with a plurality of relatively large openings into which portions of the friction material flowed to form key plugs when a lamina of friction material was molded and bonded simultaneously onto the shoe surface. This latter procedure, as disclosed in U.S. Pat. Nos. 1,696,821 and 3,513,950 however, was also beset with various shortcomings; namely, the plugs were ineffective in resisting high shearing forces after the bonding adhesive succumb to elevated temperatures. Secondly, the thickness of the friction material lamina was non-uniform resulting in manufacturing problems. Thirdly, the ideal molding conditions frequently conflicted with ideal bonding conditions requiring compromises in processing and a frequent need to add a marriage layer of a third material between the lamina and the shoe surface. Other friction applications presented similar problems. Attachment limitations prevent many clutch and brake materials with energy capacity between that of normal organic materials and fully sintered or brazed materials from working. In some drum lining applications, the combined use of both riveting and bonding was not structurally adequate.